After new ad campaigns promoting the quality of its food failed to spark sales, the parent company of Olive Garden and Red Lobster is retooling its strategy to attract diners with more promotional deals. The shift comes after Darden Restaurants Inc. moved to update the image of its flagship chains and appeal to younger diners. In its fiscal second quarter, Darden earned $33.6 million, or 26 cents per share, compared with $53.7 million, or 40 cents, a year ago.